They do increase your opponents defense. It is called balance. The stun last longer than most, and in the time they are stunned you could kill them. Due to the increased defenses that isn't the case.

Also there are many international players in DBO, you just think making and authenticating netmarble accounts are hard because you are an ignorant noob, who has never played a korean game before. Don't start now if it is just cause of DBO.

Candy makes the target immobile while they are immune to Spiritual attacks (technically) but physical attackers can still bash them. The class who uses the Candy is a Physical attacker so they have no problem.

Vise Versa to the Stone form.

I'm pretty sure I answered this type of question somewhere, only I dunno which post it was.